1. Field of the Invention
The present invention relates to non-peptidic amino derivatives, their therapeutic use, as well as pharmaceutical compositions comprising these derivatives. In particular, the invention relates to cyclic and acyclic alpha- and beta-aminocarboxamides, more particularly to tetrahydroisoquinolinecarboxamides, piperidinecarboxatnides, pyrrolidinecarboxamides, and 2-amino-3-carboxamidopyridine derivatives. The compounds of the invention possess activity as Follicle Stimulating Hormone (FSH) agonists and are useful in the treatment of infertility.
2. Summary of the Related Art
Annually in the U.S. there are 2.4 million couples experiencing infertility that are potential candidates for treatment. Follicle stimulating hormone, either extracted from urine or produced by recombinant DNA technology, is a parenterally-administered protein product used by specialists for ovulation induction (OI) and for controlled ovarial hyperstimulation (COH). Whereas OI is directed at achieving a single follicle to ovulate, COH is directed at harvesting multiple oocytes for use in various in vitro assisted reproductive technologies (e.g., for in vitro fertilization). Clinical use of preparations containing FSH began in the 1960's.
Follicle stimulating hormone (FSH) is a pituitary-derived heterodimeric glycoprotein hormone that shares structural similarities with luteinizing hormone (LH) and thyroid stimulating hormone (TSH), both of which are also produced in the pituitary gland, and chorionic gonadotropin (CG), which is produced in the placenta. The hormones are relatively large (28-38 kilodaltons) and are composed of a common a subunit non-covalently bound to a distinct .beta. subunit that confers receptor binding specificity.
The cellular receptors for these hormones are known to be members of the G protein-coupled class of membrane-bound receptors, which when activated stimulate an increase in the activity of adenylyl cyclase. This results in an increase in the level of the intracellular second messenger adenosine 3',5'-monophosphate (cAMP), which in turn causes increased steroid synthesis and secretion. Hydropathicity plots of the amino acid sequences of these receptors reveal three general domains: (1) a hydrophilic amino-terminal region, considered to be the amino-terminal extracellular domain, (2) seven hydrophobic segments of membrane-spanning length, considered to be the transmembrane domain, and (3) a carboxy-terminal region that contains potential phosphorylation sites (serine, threonine, and tyrosine residues), considered to be the carboxy-terminal intracellular or cytoplasmic domain. The glycoprotein hormone receptor family is distinguished from other G protein-coupled receptors, such as the .beta.2-adrenergic, rhodopsin, and substance K receptors, by the large size of the hydrophilic amino-terminal domain, which is involved in hormone binding.
The FSH receptor is expressed on testicular Sertoli cells and ovarian granulosa cells. While there has been a recognized need for providing essentially pure human FSH receptor, purification of naturally derived preparations is not practical and would likely be insufficient to permit determination of the amino acid sequence. Recently, one group has cloned the cDNA encoding the rat FSH receptor, deduced the amino acid sequence, and expressed it in mammalian cells (Sprengel, Mol. Endocrinol. 4: 525 (1990)). Another group, attempting to clone the TSH receptor, apparently also cloned and identified a portion of the transmembrane region of the human FSH receptor (Parmentier, Science 246: 1620 (1989)).
Use of FSH is limited by its high cost, lack of oral dosing, and need of extensive monitoring by specialist physicians. Hence, identification of a non-peptidic small molecule substitute for FSH that could potentially be developed for oral administration is desirable.